LLM Docs Nits (#17999)

docs/docs/examples/llm/openai.ipynb

docs/docs/getting_started/starter_example.md

docs/docs/understanding/using_llms/using_llms.md

...dex-llms-openai-like/llama_index/llms/openai_like/base.py

...grations/llms/llama-index-llms-openai-like/pyproject.toml